409 
difference, however, easily explained by the circumstance of 
the former chemist not having taken the necessary steps for 
purifying perfectly the liquid he examined. 
As a very unusual coincidence it may be observed, that 
the specific gravity of the vapour of potato oil, as obtained 
by Dumas, is 3.147, or but unity in the second place of deci- 
~ mals greater than has resulted for the corn spirit oil from Dr. 
Apjohn’s experiments. The oil therefore of Pelletan and 
Dumas is not, as is generally supposed, peculiar to potato 
spirit, but occurs also in that developed by the fermentation 
of the cerealia. From this latter source also it admits of 
being obtained in great quantity. When first observed by 
Mr. Coffey at Sir Felix Booth’s, there was an inch of it in 
the faint receiver ; and from the diameter of this vessel he 
estimated its total amount to be at least fifty gallons. This 
is the quantity produced at that establishment every fort- 
night, the excise laws compelling the distiller to distil and 
brew alternately, and about a week being consumed in each 
process. 
The whiskey manufactured some years ago contained, 
Dr. Apjohn observed, a considerable quantity of this oil, and 
owed to its presence a great deal of the pungency of taste 
and smell by which it was distinguished. From the nature 
of the still at present generally used, but a small por- 
tion of this substance passes over; and hence the reason why 
the spirit now made is, as compared with the product 
of the old processes, less disagreeable to the palate, and pro- 
bably less injurious to the constitution. It is undoubtedly 
owing to the same cause, (an improvement in the process 
of distillation,) that this oil has at length been noticed in the 
distillers’ faints. Upon the old system of manufacture the 
greater portion of it was driven over, and was held dissolved 
by the spirit into which it was thus introduced ; but with the 
modern stills, particularly that devised by Mr. Coffey, no- 
thing having so high a boiling point as this oil, can by pos- 
